1. Field of the Invention
This invention generally relates to a seatpost that is adjustable to change a seat height of a bicycle seat.
2. Background Information
A bicycle seat is normally supported on a bicycle frame by a seatpost that is telescopically disposed in the seat tube of the bicycle frame. The bicycle seat typically has a pair of parallel rails extending along the bottom of the seat. The rails of the bicycle seat are attached to the seatpost by a clamp at the top of the seatpost. The height of the bicycle seat with respect to the bicycle frame is typically adjusted by changing an insertion amount of the seatpost in the seat tube of the bicycle frame. The upper end of the seat tube is typically provided with a longitudinal slit and a clamping arrangement that adjusts the diameter of the upper end of the seat tube to squeeze the seatpost for securing the seatpost in the desired position with respect to the bicycle frame.
Recently, seatpost have been proposed that various adjustment mechanism in order to adjust the height of the seat. In some conventional mechanical bicycle seatpost adjustment mechanisms, a manual lever is provided for changing the seat height using a piston type telescopic tube arrangement such as disclosed in U.S. Pat. No. 7,083,180. Also motorized seatpost assemblies have been proposed for changing the seat height. Examples of motorized seatpost assemblies are disclosed in Japanese Laid-Open Patent Application No. 2005-231567 and Japanese Laid-Open Patent Application No. 2005-262900. In these motorized seatpost assemblies, when the rider sit down the seat, the force is transmitted to the height adjustment mechanism, which impart undesirable stresses on the height adjustment mechanism.